BMW 8 Series AUC Sensor Causing Air Circulation Issues

Hey there! I have some experience working on cars and went through something very similar with my 2021 BMW 7 Series. The symptoms were exactly like yours, nasty smells coming in and blower issues. Took it to my trusted workshop and they found it was just a loose connection in the AUC sensor wiring harness. They had to remove some panels to access it, but basically just needed to reseat and secure the connections properly. The whole thing cost me 95 Euro and has worked perfectly since then. Before I share more specifics, could you tell me if you're getting any other warning lights or errors besides the AUC sensor? Also, does the issue happen all the time or only in certain conditions? This info would help me confirm if it's the same problem I dealt with. My actually had a similar issue with his BMW 5 and it turned out to be something different, so best to get all the details to point you in the right direction.

Hey, thanks for your detailed response! My BMW has about 184305 KM and was last serviced 2 months ago. No other warning lights showing up actually, and the issue seems to happen consistently whenever I'm in slow-moving traffic. The smell gets really bad when I'm behind trucks or buses. The service center did a computer diagnostic but didn't spot anything else unusual besides that AUC sensor error. It's reassuring to hear your fix was relatively straightforward and affordable. I'll definitely mention the wiring harness possibility when I take it in.

Yeah, that definitely sounds just like what I experienced! When my BMW 7 was showing these symptoms at around 170K km, I also noticed the smell was worst behind diesel vehicles. The fact that you're getting it consistently in traffic and the error is isolated to just the AUC sensor really points to the same wiring issue I had. Just to share a bit more about my experience, after they fixed the loose connection, they actually recommended cleaning the entire ventilation system as preventive maintenance. The mechanic explained that when the AUC sensor isn't working properly for a while, all sorts of stuff can build up in there. I went ahead with the cleaning and honestly noticed a huge improvement in the overall air quality. Quick tip though, after they fixed mine, I started paying more attention to when I manually switch to recirculation mode, especially in heavy traffic. Even though the automatic system works great now, I like having that extra control just in case. Have you noticed if manually switching to recirculation mode makes any difference? In my case, it didn't work either way until they fixed the wiring, but it might help narrow down the exact issue for your mechanic.

Thanks so much for all this helpful info! Actually, I tried the manual recirculation switch multiple times but it doesn't make any difference, just like your situation before the repair. Really good to know about the ventilation system cleaning too. I hadn't thought about potential buildup during the time the sensor wasn't working properly. I'll definitely ask about getting that done when I take it in. I've already made an appointment with my mechanic for next week. I'll make sure to mention both the wiring harness connection check and the ventilation system cleaning. It's such a relief to hear this is likely a straightforward fix and not something major. I've been worried about potential expensive repairs, so knowing it might just be a loose connection is really reassuring. I'll update the thread once it's fixed in case anyone else runs into the same issue. Thanks again for sharing your experience!